Test plates for chemical or biochemical analyses, or sample preparation and purification, which contain a plurality of individual wells or reaction chambers, are well-known laboratory tools. Such devices have been employed for a broad variety of purposes and assays, and are illustrated in U.S. Pat. Nos. 4,734,192 and 5,009,780, 5,141,719 for example. Microporous membrane filters and filtration devices containing the same have become particularly useful with many of the recently developed cell and tissue culture techniques and assays, especially in the fields of virology and immunology. Multiwell plates, used in assays, often utilize a vacuum applied to the underside of the membrane as the driving force to generate fluid flow through the membrane. Centrifugation also can be used. The microplate format has been used as a convenient format for plate processing such as pipetting, washing, shaking, detecting, storing, etc.
Typically, a 96-well filtration plate is used to conduct multiple assays or purifications simultaneously. In the case of multiwell products, a membrane is placed on the bottom of each of the wells. The membrane has specific properties selected to separate different molecules by filtration or to support biological or chemical reactions. High throughput applications, such as DNA sequencing, PCR product cleanup, plasmid preparation, drug screening and sample binding and elution require products that perform consistently and effectively.
One such filtration device commercially available from Millipore Corporation under the name “Multiscreen” is a 96-well filter plate that can be loaded with adsorptive materials, filter materials or particles. The Multiscreen underdrain has a phobic spray applied in order to facilitate the release of droplets. More specifically, the MultiScreen includes an underdrain system that includes a spout for filtrate collection. This spout not only directs the droplets but also controls the size of the droplets. Without the underdrain system, very large drops form across the entire underside of the membrane and can cause contamination of individual wells. Access to the membrane can be had by removing the underdrain. However, the device is not compatible with automated robotics equipment such as liquid handlers, stackers, grippers and bar code readers.
The Society for Biomolecular Screening (SBS) has published certain dimensional standards for microplates in response to non-uniform commercial products. Specifically, the dimensions of microplates produced by different vendors varied, causing numerous problems when microplates were to be used in automated laboratory instrumentation. The SBS standards address these variances by providing dimensional limits for microplates intended for automation.
It would therefore be desirable to provide a multiplate format that is in compliance with the SBS standards, yet maximizes well volume and is compatible with both vacuum and high speed centrifugation.
It also would be desirable to provide a multiplate format that is a one-piece design having high rigidity capable of withstanding high centrifugal load.